Operations - How to Create a "String Diagram"

[jecorbett]

As someone who used to program mainframe computers for a living, I can tell you something one of our IBM reps said to me that really stuck in my head. Computers are a great tool for doing one thing a million times. They are a lousy tool for doing a million things once. In other words, computers are ideal for doing repetitive tasks but require a great deal of up front programming time that only has a payoff if the final program is going to be used over and over again. Now we did most of our programming from scratch so it is a little different with packaged software such as Excel where the basic program has already been developed. Still, you should ask yourself a question. Could you create your string diagram with pencil and graph paper in less time than it is going to take you to figure out how to do it with Excel.

[billbtrain]

I've managed to create a schedules chart using Excel 2007.This program allows a user to save a copy as a Excel 1997-2003 compatable file.If anyone is interested in viewing or creating a chart for operations or just to view schedules as a chart as I did with the Great Northern November 1969 schedules,let me know.

Have a good one.

Bill B

[billbtrain]

I am no computor guru but don't you need to introduce speed and disstance to put it all on a graph? Then after you graph all or some trains you could then put it into a sequential schedule. The graph will not be the finished product, correct?

Am I in left field here?

Miles and times with the train numbers as string lines on the graph.Yes,the graph is the finished product.Easy to do with paper and pen,but on the computer?

Most people work out schedules for their MR,I'm trying to graph the trains operated by the real Great Northern to plot meets and such.

Disclaimer:freight trains of the 60's onward didn't operate on schedules.Even tho they had schedules published for freights in the Official Guide.

Have a good one.

Bill B

[spidge]

I am no computor guru but don't you need to introduce speed and disstance to put it all on a graph? Then after you graph all or some trains you could then put it into a sequential schedule. The graph will not be the finished product, correct?

Am I in left field here?

[billbtrain]

Anybody have any ideas for making string graphs using free download software?  I've been trying to make graphs using MS Works Spreadsheet and come up with nothing.

Have a good one.

Bill B

[billbtrain]

I'm starting to do some "operations" on both my home and Club layout.  As part of the planning for conducting my first "ops session" I'd like to do a "String Diagram" to plot out where my meets will be.  I've tried to create such a diagram by first using Excel (spreadsheet program) to layout on the X axis (horizontal) the time and the Y axis (vertical) the station stop.  I then enter , by Train #, the time a train will be at each location.  However, when I try to use the graphing feature in Excel I cannot get the stations to be on the Y axis.  If anyone has been able to use Excel to create a "Sting Diagram" please let me know how you did it.  Thanks.

Have you had any luck? I'm trying to do the same thing with prototype schedules and the program won't do it.

Have a good one.

Bill B

[Texas Zepher]

That's the way Excel normally plots things.  However, you can use the "Scatter Diagram" option in the graph choices to actually use the X-axis values.  Otherwise it will assume that the X-axis items are evenly spaced and monotonically increasing.

True but using x,y charts introduces some new and different problems.  For example when one wishes a train to change directions.  This is easily fixed by having a completely different set of coordinates for each train.  It doesn't look pretty in the spreadsheet but if the only goal is to generate the string diagram that shouldn't be an issue.  Another problem with x,y charts is labeling the stations.  Once again this can be overcome by overlaying a second line or bar chart on top of the x,y with the labels defined as the station names.  I have never done an x.y chart with time as one of the coordinates.  I have no idea what it will put as lables. 

That brings up another consideration I haven't seen anyone mention.  If the time goes over noon or midnight something will have to be done to compensate for the new PM or day.  Going to 24 hour designation would help if one is going to only run a single day schedule.

[MisterBeasley]

The other problem is Excel will always evenly space the values along the X axis, so your trains can only arrive and depart stations at evenly spaced time intervals.

That's the way Excel normally plots things.  However, you can use the "Scatter Diagram" option in the graph choices to actually use the X-axis values.  Otherwise it will assume that the X-axis items are evenly spaced and monotonically increasing.

[nbrodar]

If you can lay your hands on it, the June 1995 MR has an article about using Excel to create a timetable and string diagrams.

Nick

[steveb]

It sounds like you are in the early stages of operation on your layout.  Don't try to make a string diagram or even a hard and fast timetable.  For the first 10 op sessions note either in real time (if using sequential trains) or in fast time the amount of time each train spends from its origin to destination.  Over the first few sessions, this time will vary quite a bit until your operators get familiar with how trains run over your railroad.  After 10 op sessions you will notice that the times settle down.  Then you can plot a string diagram.  I just use graph paper and pencil.  On the other hand you may find you have to modify your timetable because of unexpected traffic jams which turns your railroad into a large parking lot or other reasons such as the classification yard is overwhelmed.  I have had operations on my layout for about 14 months and I am on my 3rd timetable.  As for balancing car cards/waybills if you are using that system, that is another worthwhile discussion but not for this thread.

Steve B.

[Dave-the-Train]

The good news is that when a real railway wants to make a whole new timetable (or even a major revision) it takes a big team of humans a year or two to figure it out.  Then they have to check it through.  Computers tend to be rubbish at this.  As far as I can tell RR timetables are the worst for computers/programmes because of their three dimensions only one is variable... that is trains can only go forward or back and - to a lesser etent - sideways... so everything ends up hanging on the third dimension of time.  If time and timings were constant it might work out but they vary enormously.

trains run at different speeds

section lengths vary

section times vary due to different grades and curves

then there's yard times/station times

That's just some of it.

For your own enjoyment the best thing to do is probably to map out a sequence without too much concern about time.  in real life trains have to sit and wait for opposing and conflicting trains to clear ... and for following faster ones to overtake.

Trains also end up having to wait for yard roads to be free for them to get in off the main... this backs up the main...  I don't know but I suspect that we would be looking at some sort of diagram system that showed every length of track/section/siding with an "occupied"/"free" marker - and put all that against a time line...

[I once tried choreographing the train movements on a layout using a variation of Benesh (spelling?) Notation - the scheme they use to show what moves ballet dancers make, where and when on stage.  the idea was great... the realisation... well, let's just say that it dawned on me that I could model trains or figure out movements.  I also realised that if I ever did complete the scheme I would have to get other people to learn how it worked and apply it...]

Timetable planning is a full time and lifetime career.

If you start with a simple sequence you will probably begin to get a better idea of what is going on.  this will help you fit the information to a programme, persuade you to give up the idea or (hopefully) encourage you to work it out the real way with pen and paper.

If you plan a TIME table you also run into issues of time... real time or speeded time... what to do?  What will other people do... Stop the clock when they tie up?  Clubs have fallen apart rowing over this.

With a sequence you can specify that trains meet at locations... much like Train Order working... If you need in a club you can designate a despatcher who will decide what happens if Fred's train is running late...

Hope this isn't too discouraging and helps.

PS... if you do actually work out a programme that really does work you could end up rich

PPS. Of course , once you have the perfect timetable a car will derail or a loco break down and throw a spanner in the works...

[Anonymous]

Take your towns and sidings.

For example I might have three towns where my trains can pass each other.

I will draw a big tic tac toe type diagram on paper.

 

 

Now.

My yard and my Staging are not on this chart. For purposes of clarity I can assign the yard to the left side and staging to the right side because that is how the trains must travel to get to the yard where they are broken down into locals to the three towns. 

Who cares how many towns? How many mile posts? How many sidings? You can add fewer squares or many squares running trains down to 10 minute values in between 50 towns across 120 miles in a 24 hour period.

Such a huge chart will be a frankenstien and be a dispatcher's night mare as soon as one train starts to run late.

In my case, my time slots are a nice generous 6 hour blocks of time. Most charts Ive seen are cut down to 15 minute blocks on a much longer sheet. As the day progresses a dispatcher might have a line starting for each train generated and marked off as it progressed across a territory.

If.. in town one first thing in the morning the Mine run is returning to the yard with a load of coal waiting in the siding. The meet would be arranged so that when my Local arrives there from the yard, the mine train will be clear to finish the meet and proceed to the yard.

I run sequence operation, one train at a time. When you throw in two or more operators this plan starts to suffer a sort of load that takes away availible siding capacity. Obviously if the chart is full and a new train is sortied ... let's call out the big hook to fix the wreck in town two... it's going to potentially melt down the system.

There might be other meets scheduled for later in the day.

That is the best I can do for now, I will learn more about this hopefully as others contribute thier ideas about diagramming meets in time and space.

As far as I know this system works with any size railroad, ignoring for the moment the awful fact that a caboose on someone's train might still be in the last town visited.

[Texas Zepher]

I'd like to do a "String Diagram" ... using Excel (spreadsheet program)
X axis (horizontal) the time
Y axis (vertical) the station stop.
by Train #, the time a train will be at each location. 

I cannot get the stations to be on the Y axis.

You have to assign the stations numbers which will plot to become the Y value. Time and Date do not plot well.  Then assign the labels for the Y axis separately.

The other problem is Excel will always evenly space the values along the X axis, so your trains can only arrive and depart stations at evenly spaced time intervals.

One way around both of these problems is to define the Y axis by milepost.  Put station labels on the appropriate mile posts.   Then schedule the trains by which mile post they are supposed to be at every each interval.  The time intervals can be as course or fine as you want the chart to be.     

[leighant]

I started to answer this and then realized I need to think this through.  Let's see, putting the time a train will be at each location will not work unless trains never stop.  If a train stops at a location and then proceeds, it is at that location for the time of arrival and the time or departure and all the time in between. 

On the other hand, at any given time, a train can be in only one place (discounting that our short mainlines allow the loco to be in town A while the caboose is in town B!)  Data could be entered for time, with the location (milepost for instance) to be given for where the train is at that moment.

4pm train is at Neola (MP 20)

4:15 train is at 65th St Yard (MP 15)

4:25 train is at Santa Vaca (MP 12) making a station stop.

4:35 train is STILL at Santa Vaca (MP 12) and leaving.

4:45 train is at STUB Jct. (MP 10)

4:48 train is at Niedner (MP 8)

4:53 train at Tidelands (MP 5) (arriving)

4:48 trains at Tidelands (leaving)

4:52 train at Bay Point (MP 3)

5:00PM train at Karankawa Union Station (MP 0)

Or is this what you already did?

[MontRailLink]

I'm starting to do some "operations" on both my home and Club layout.  As part of the planning for conducting my first "ops session" I'd like to do a "String Diagram" to plot out where my meets will be.  I've tried to create such a diagram by first using Excel (spreadsheet program) to layout on the X axis (horizontal) the time and the Y axis (vertical) the station stop.  I then enter , by Train #, the time a train will be at each location.  However, when I try to use the graphing feature in Excel I cannot get the stations to be on the Y axis.  If anyone has been able to use Excel to create a "Sting Diagram" please let me know how you did it.  Thanks.